When screenwriters and authors portray men as full-time fathers, many follow a simple rule: Play it for laughs.

It has been 20 years since the movie "Mr. Mom" regaled audiences with a stay-at-home dad named Jack, who bumbled his way through diapers, discipline, and such domestic terrors as a runaway vacuum and an overflowing washer.

Now Jack's 21st-century counterparts are arriving, and similar humor prevails. The movie "Daddy Day Care" opens this weekend, starring Eddie Murphy as an unemployed father who starts a "guy-run" day-care center with a buddy. The "Mr. Mom" formula remains firmly in place: Men + kids = laughs galore.

That theme also runs through two new books by at-home fathers. In both, Dad cares for the kids while Mom works to support the family. Publishers describe these books as "hilarious." Producers use the same adjective for "Daddy Day Care," along with "sidesplitting."

Real-life families have changed considerably since "Mr. Mom" appeared, with more men sharing child-rearing and household chores. But public portrayals often remain stuck in stereotypes of hapless domesticated dads. That image rankles some men in real-life role reversals, who think the laugh-track approach demeans what they do.

"It's almost as though the media want us to think of them as bumbling fathers, but they're not," says Peter Baylies, founder of the At-Home Dad Network.

A report released this week by the Council on Contemporary Families finds that American men do more housework and child care than men in any of the other four developed countries surveyed: France, Italy, Germany, and Japan.

Finding humor in parenthood is nothing new, of course. Erma Bombeck played motherhood for a million laughs. And as Scott Coltrane, a professor of sociology at the University of California, Riverside, notes, "Comic, inept dads have been around for a long time."

In the late 1970s and early 1980s, a number of "househusband" books were published, many written by reporters taking a year off. "There's now kind of a genre for the new dad: the involved, nurturing father, celebrating the joys of actually being a parent," he says.

Popular culture both honors and makes fun of men in families, Professor Coltrane says. "Cultural images feed off men's and women's anxieties over changing gender and parenting roles."

He describes "contradictory tensions" in cultural stereotypes. "In one, men are bumbling idiots - they can't do anything. In the other, men are capable, nurturing, caring, and loving people. Both are addressed to women. One makes women feel good because he's a bozo and can't do it. The other is more a wish fulfillment that there actually are men out there who are kind, caring, sensitive, even sexy."

David Eddie, author of the just-published "Housebroken: Confessions of a Stay-at-Home Dad" (Riverhead, $14), playfully calls himself "Cinderfella" and a "faceless drudge." He takes his toddler son to his favorite watering hole with him, and leaves him at a lingerie shop called Nearly Naked, in the care of the owner, a friend, while he runs errands.

Similarly, in the forthcoming "I Sleep at Red Lights: A True Story of Life After Triplets" (St. Martin's, $24.95), Bruce Stockler describes himself as "an anomaly, like a mermaid or an anarchist." The stay-at-home dad, he writes ruefully, is "a socially awkward reality in the suburbs." Yet, ever the humorist, he goes for laughs as he describes taking his three young sons and daughter to the ladies' room at a shopping mall, because it was cleaner than the men's room.

Mr. Baylies speculates that humor in these movies and books helps to counter deep ambivalence about role reversals. "The real changes in families might not be what the public wants to hear," he says. "Maybe we're afraid to lose the notion that moms aren't always going to stay home. There's always that masculinity thing that Dad wants to hold on to, that macho image. It's hard to give up. It's so ingrained in us. I don't think the public wants to let it go. But it's happening gradually."

Baylies, of North Andover, Mass., sees heartening signs of progress, from changing tables in McDonald's men's rooms to play groups for at-home fathers and their children. He has cared for the couple's two sons, now 11 and 8, since he was laid off as a software engineer in 1992. His wife teaches school.

One self-described househusband in southern California, a former lawyer who wants to be identified only as Mark, has been home with the couple's three sons for nearly 10 years. He calls entertainment-media images of men like himself "clichéd" and "superficial," adding, "There is depth to what we're doing."

In American society, he says, "there's not much left in terms of what it's OK to poke fun at. Jokes about women, ethnic groups, and gays are frowned on. But men at home remain fair game."

Still, he remains hopeful that as more men assume new roles, "we will eventually reach a crossover point where it won't be that funny anymore."

As fictional househusbands and real-life at-home fathers grapple with doubts, fears, and guilt about their unconventional roles, they also find themselves redeemed by family life. The eternal verities of parenthood bring satisfaction: It's hard work, but it's rewarding, too.

No wonder these "sidesplitting" movies and "hilarious" books specialize in heartwarming endings. "I look upon taking care of him as a crucial step in my spiritual path, in my development as a human being," Mr. Eddie writes.

Echoing that theme, Mr. Stockler says, "I love my children fiercely."

Mark, too, finds unexpected rewards. "You're an easy target for ridicule, but you're also an easy target for people to praise you and tell you you're great," he says. "What I do is no different from what mothers have always done. But I get a lot more credit."